Loss And Loss Adjustment Expense Reserves (Schedule Of Company's Second-Lien RMBS Exposure, Gross Undiscounted Claim Liability And Potential Recoveries, Before The Elimination Of Amounts Related To Consolidated VIE's) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Loss And Loss Adjustment Expense Reserves [Line Items]
Outstanding Gross Principal	$ 14,264	[1]	$ 15,257	[1]
Gross Interest	8,632	[1]	8,361	[1]
Gross Undiscounted Claim Liability	1,235		1,589
Potential Recoveries	1,085		4,109
Insured Issues Designated As Classified List [Member] | Non Variable Interest Entities [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Issues	23
Outstanding Gross Principal	3,400
Gross Interest	1,300
Gross Undiscounted Claim Liability	200
Potential Recoveries	800
Insured Issues Designated As Classified List [Member] | Variable Interest Entity Primary Beneficiary [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Issues	11
Outstanding Gross Principal	1,700
Gross Interest	600
Gross Undiscounted Claim Liability	100
Potential Recoveries	$ 600

[1] Represents contractual principal and interest payments due by the issuer of the obligations insured by MBIA.